Conventionally, an electronic control device includes a fuse in case of a fault in the electronic control device. In an electronic control device in which small components are densely arranged, because a short-circuit current generated at a short-circuit fault in the small components does not reach a high current, it takes a long time to interrupt by the fuse. Especially when a large fuse is used for protecting a plurality of electronic control devices so as to reduce the number of fuses and a cost, it takes a longer time. Thus, temperatures of the components may be increased at an interruption and a voltage drop in a power supply wire and the like may be caused for a long time. In contrast, in a common wire, such as a power supply wire (e.g., a battery path and a ground path), that supplies electric power required for operating many circuits and many components mounted in accordance with advancement and diversification of electronic control, a relatively high current flows. Thus, an interrupting current of a large fuse disposed in a common wire path is further increased, and the electronic control device does not secure a sufficient interruption performance at a short-circuit fault in each circuit or each component. The above-described issue becomes noticeable, for example, in an electronic control device for a vehicle used at a higher temperature and including many mounted devices.
JP-A-2007-311467 discloses a printed circuit board control device in which an interrupt wire is disposed in a power supply wire in each substrate. If an overcurrent flows, the interrupt wire melts and the power supply wire is interrupted in each substrate or each device.
On a substrate in which components are densely mounted, a component-mounted wire, such as a land, on which an electronic component is mounted, and a common wire shared by the electronic component and a plurality of other electronic components are disposed adjacent to each other. Thus, heat generated at melting of the interrupt wire may be transmitted to the other electronic components through the common wire and the heat may have adverse effects on other electronic components. For example, a solder that couples the common wire and one of the electronic components may be melt by the heat.
In addition, on a substrate in which components are densely mounted, a wire, such as a land, on which an electronic component is mounted, and a plurality of other electronic components are disposed adjacent to each other. Thus, when an interrupt wire is simply provided to the wire, high temperature generated at the interrupt wire by an overcurrent may be transmitted to the adjacent electronic components, for example, via the substrate, and the adjacent electronic components may be subjected to the high temperature. As a result, adverse effects such as a decrease in performance and a decrease in life may be caused in the adjacent electronic components. In particular, in cases where characteristics of the electronic components change with temperature, the electronic components may operate abnormally.